[ty] Fix ParamSpec declaration hover and type navigation (#27183)
## Summary
Fix hover and go-to-type-definition on PEP 695 `ParamSpec` declarations
by resolving the declared parameter's inferred type in the shared IDE
target resolver.
## Test plan
- Existing hover regression confirms a declared `ParamSpec` now displays
its inferred type and variance.
- Existing navigation regression confirms go-to-type-definition resolves
the declared `ParamSpec`.
